1. Field of the Invention
This invention relates generally to industrial ball valves. More particularly, this invention pertains to the use of epoxy to secure the housing seat to the housing of a ball valve.
2. Related Art
Various types of valve seats are utilized in ball valves. In most ball valves, an annular housing seat is fixed in position relative to the housing of the valve. The housing seat is configured to engage against a portion of a pivotally movable plug or gate when the gate is in the closed position. In large industrial ball valves, the housing seat is typically a replaceable part. When installing a housing seat within a large industrial ball valve, either as an original or replacement seat, it is often necessary to perform a step of adjusting the alignment of the housing seat to ensure that full annular contact is made between the housing seat and gate seat when the gate seat in the closed position. Adjustment may also be necessary to ensure that there is sufficient and uniform compressive contact pressure such that, at full head pressure, fluid will not pass between the seals. To this end, it is known to align the housing seat relative to the housing using a plurality of pushing and pulling screws spaced circumferentially around the annular housing seat. The pushing and pulling screws allow the housing seat, which is typically metal, to be slightly deformed and allow for subtle changes in the orientation of the housing seat relative to the housing. This allows for the adjustment of the contact area and pressure between the housing seat and the gate seat. Once the housing seat is aligned, the screws are locked in place and the ball valve can be put into service.
While the above-mentioned method of aligning and supporting a housing seat within a ball valve has utility, there are some disadvantages to such prior art methods. A primary disadvantage is that the screws exert non-uniform loads on the housing seat and, as a result, over time tend to cause the sealing surface of the housing seat to warp as a result of the uneven loading exerted thereupon. While such warpage may be slight and, at least initially, does not affect the sealing capability of the ball valve, it can lead to premature seal failure.